Diphenols, otherwise known as bisphenols, are well-known in the art and are commonly used in the preparation of polycarbonates, polyesters, polyester-carbonate copolymers and other polymers and copolymers. It is well-known that by varying the structures of the monomers used to make the foregoing polymers and copolymers, substantial changes in various properties can be realized, such as changes in impact strength, toughness, transparency, heat distortion limits, dimensional stability, creep resistance, flame-retardancy and the like. It is also desirable to improve such properties, where possible, by changing or altering the structure of monomers used in the polymers or copolymers, and accordingly, it is desirable to provide new and improved monomers to improve the properties of the resultant polymers. Polycarbonate compositions having improved flame-retardance are disclosed in U.S. Pat. No. 4,182,838 where halogenated vinylidene diphenols are used to prepare high molecular weight aromatic polycarbonates. Other halogenated polycarbonates have also been obtained by using halogenated monomers as the main polymer building block. Examples of such polycarbonate compositions include those derived from tetrabromobisphenol-A and tetrachlorobisphenol-A monomers as disclosed in U.S. Pat. No. 3,028,365.
Fluorine-containing polyarylates are described in a paper published in Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1649-1654, September, 1965, (Chemical Abstracts 64, 8321h (1966). Homogeneous and mixed terephthalic, isophthalic, and the like, polyesters of 4,4'-(hexafluoroisopropylidene)diphenol monomer and of 4,4'-[alpha-(trifluoromethyl)benzylidene]diphenol monomer were synthesized, and it was found that the replacement of CH.sub.3 groups on the central carbon atom of the isopropylidene diphenol and the methylene diphenol by CF.sub.3 groups leads to a lowering of the softening points of homogeneous and mixed polyesters based thereon. Similar monomers are described in Netherlands patent application Ser. No. 6,407,548 filed July 2, 1964, and opened for inspection on Jan. 4, 1965. The Netherlands disclosure relates to a process for the preparation of polycarbonate resin by reacting phosgene with 2,2-bis(p-hydroxyphenyl)-1,1,3,3-tetrafluoro-1,3-dichloropropane monomer. The polycarbonate resin was characterized as having very good thermal stability and low vapor permeability. The monomers in the foregoing references were prepared from the corresponding phenol, and in all cases, the positions on the central carbon atom of the diphenol have been substituted with trifluoro- or chlorodifluoromethyl groups or a chlorodifluoro methyl group in combination with a phenyl group.
In U.S. Pat. No. 3,388,097, liquid 4,4'-(1,1,1-trifluoroethylidene)diphenol monomer was made from trifluoroacetaldehyde hydrate and phenol in the presence of anhydrous hydrogen fluoride at 50.degree. C. for 8 hours in a Hastelloy bomb. The liquid product was distilled under reduced pressure at 165.degree.-170.degree. C. and 0.5-0.6 mm. Hg and was obtained in 40% yield. Polyesters were made from these perhaloalkyl bisphenols and specified aromatic acid halides. However, it is noted that the acid catalyst used in making the diphenol is anhydrous hydrogen fluoride; that the reaction is carried out in a "bomb" so as to withstand the considerable autogenous pressure of anhydrous hydrogen fluoride that exceeds 40 to 150 lbs/in..sup.2 at the required reaction temperatures; and that the reaction product distills at 165.degree.-170.degree. C. at reduced pressure. The bisphenols from which the polyesters of U.S. Pat. No. 3,388,097 are made, have the structure: EQU HO--Ar.sub.1 --Z--Ar.sub.1 --OH (1)
wherein Ar.sub.1 is para-phenylene, and Z is a divalent radical having the formula: ##STR1## wherein R and R' may be the same or different and represent perhalogenated lower alkyl groups, fluorine and chlorine being the preferred halogen species, with the provision that R' may represent hydrogen when R represents a perfluorinated lower alkyl group. In U.S. Pat. No. 3,388,097, it is disclosed that these bisphenols or diphenols are prepared by the acid catalyzed condensation of an appropriate halogenated ketone or aldehyde with two molecules of an appropriate phenol. However, as disclosed above, the acid was hydrogen fluoride gas, and there is no suggestion of solid fluorinated diphenols, or of polycarbonates, or of improved flame retardance of the polyesters derived from the fluorinated diphenols or of a non-pressurized or low pressure gaseous acid catalyst system.
Other halogenated diphenols are disclosed in U.S. Pat. No. 2,435,014 and are obtained by condensing two moles of a t,t-octyl-phenol or -naphthol with 1 mole of a polyhalogenated carbonyl compound, and the condensing agents are a mixture of concentrated sulfuric acid-acetic acid and hydrogen chloride-acetic acid. The polyhalogenated carbonyl compounds claimed in making the condensation products in U.S. Pat. No. 2,435,014 are chlorine, bromine or iodine and the examples illustrate chlorine only as a substituent.